The growth of InAs epilayers on GaAs substrates has been a subject of intense studies over the past few years, due to important device applications of such layers in optoelectronics. In the field of high-speed infrared detectors, InAs is especially attractive as an absorption layer, due to its narrow band gap and high electron mobility. On the other hand, a semi-insulating GaAs is very convenient as a substrate, due to its transparency. However, the large lattice mismatch (7.3%) between InAs and GaAs causes major problems in obtaining high quality material.
In this work we concentrate on the problem of optimization of the MBE growth of thick (3.5 - 7 μm) InAs epilayers. Three types of layers were grown: undoped, Si-doped, and Be-doped. For such layers the optimum growth conditions comprising the substrate temperature, the flux ratio, and the growth rate have been found.
The grown layers are strongly nonhomogeneous as regards morphology, and, as a result, they exhibit some spatial distribution of carrier concentration and mobility. Therefore, we analyzed the dependence of transport properties of the layers on their thickness. Special attention has been devoted to the problem of low doping with Be to obtain the p-type material of low concentration of acceptors. Such a material is very promising as an absorption layer in infrared detectors. It has appeared that in the case of InAs slightly doped with Be, the transport properties dramatically depend on the thickness of the layer.
The transport properties of the studied layers have been correlated with their structural quality studied by X-ray diffractometry.
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